US2659129A - Composite alloy - Google Patents

Description

O 1953 T. E. LEONTIS ET AL 2,659,129

COMPOSITE ALLOY Filed Aug. 16, 1950 5 n i I HVVENTUKQ Thomas E. Lean/1's BY Rober/S. BUS/C WWW constituent.

possessing its characteristic lightness.

Patented Nov. 17, 1953 COMPOSITE ALIJ'QY ThomasnE'. Leontis. and Robert S.. Busk, Midland, Mich v assig nors, to The. Dow Chemical Comepany, Midland, Mich, a corporation of Dela-- Waite.

Application August 16, 1950, Serial'No. 179 772 8.- Claims...

The invention relates to; a. composite: metal body of which magnesium the. predominant It more particularly concerns a. dieexpressed composite metallic body comprisin magnesium having alloyed therewith at-least, one solid solution-forming constituent.

Because magnesium is one. of the; lightest, as well as most. easily obtainable, oi the abundant metallic elements, and: but moderately strong, numerous attempts. have. been made to. improve its. strength and other properties, thereby: to increase its usefulness by alloying with: it other metallic; elements. As a. result, many magnesiu-m-base alloys have been made exhibitin greater strength than magnesium. itself while Nevertheless, it is an ever resent, desideratum in. the art to rovide still stronger and more corrosion resistant-magnesium-base alloys having: a wider range of uses.

The term magnesium-base alloy used herein means a magnesiumebase" alloy containing; at

not been wholly satisfactory. One of, the, difiiculties in attempting to alloy aluminum with magnesium in conventional manner in the pres.- ence" of manganese, as when the" manganese is already alloyed withmagne'sium" or is being alloyed with the magnesium at the same time as .the aluminum is being alloyed; is: that some of the. manganese either" fails toalloy or is" precipitated and settles out of the melt and is lost. Also. duringthe alloying; operatiom some of the aluminum is always lost along: with'the manganese by precipitation as: a magnesium aluminu-m compound. As: a consequence, there results an alloy in which the. beneficial'efie'cts. of

the manganese, normally realized to: the fullest extent in the binary magnesium-base; magnesium-manganese alloys, as well as the beneficial effect of alloying aluminum with magnesium, cannot be fully attained in the more complex magnesium-base. alloys containing both. man:-

.ganese. and aluminum.

It. is; the. principal obj ect. oi this: inyention to providev a. method of making. a magnesium-base alloy body containingboth manganese and aluminum which permits the inclusion in the magnesium-base. alloy body of. any amount. oimanganesewithin its range of alloyability in. magnesium. Other objects and advantages will; appear as the description of the invention proceeds.

The invention is predicated upon the discovery that; by die-expressing; the solid binary magnesiumebase magnesium-manganese alloy in, atom-,- ized form in admixture; with. the: magnesium soluble metal aluminum, in suitably: comminuted form, a. solid magnesium-base composite. metal bodyis obtained having enhanced tensile strength and other desirable properties. In addition, the method makes possible the inclusion in the die,- expressed magnesium-base composite metal body of a higher useful proportion of manganese, than is possible. in. the alloying practices heretofore employed with the, magnesium-base alloys containing manganese together with, aluminum. Also other unalloyed (elementary); magnesiumsoluble metals, in solid comminuted form, may be included in the mixture to be die-expressed, thereby still further modifying the properties of the, composite metal product.

The invention then consists of theimproved magnesium-base alloy composite metal bodyand method of makingthesame hereinafter full-y de scribed. and particularly pointed out in the claims, the following description setting forth severalmodes ofv practicing the. invention.

In carryingout, the invention, magnesium, with which manganese has been. alloyed in conventional manner is used in atomized form. The proportions of, manganese which may be alloyed with the magnesium are aboutOLl to 2-5 per cent. It. is preferable to. use about 1 to 2 per cent of manganese. If desired, small, amounts of calcium, oftentimes included in the commercial binary magnesium-base magnesium-manganese alloy, may be present in usual amounts, e. between about 0.05 and 0.5. per cent by weight of the alloy. The alloy is reduced: to particulate form preferably by atomizing:

The atomizedform may be, obtained in suitable manner as by forming a melt of the alloy and atomizing it by. impinging a jetof a cool gas, e. g. natural gas, against a thin falling stream of the molten alloy. The atomized all'oy consists of fine spherical rapidly solidified particles of the alloy with a very fine grain structure. It is desirable to screen out and reject particles coarser than those passing through 3 about a or mesh standard sieve and finer than those retained on about a 200 mesh standard sieve.

The magnesium-soluble metals including the aluminum, which may be either unalloyed (elemental) or alloyed with magnesium, with which the atomized manganese-containing magnesiumbase magnesium-manganese alloy is to be mixed prior to die-expression, may be comrninuted in any suitable way such as by atomizing in a manner similar to that described for the manganesecontaining magnesium-base alloy, if the metal admits of such atomization, or by mechanically subdividing the solid metal as with an impact, hammer, beetling, or stamping mill. The size of the particles of these metals may be similar to or finer than those of the atomized magnesiumbase magnesium-manganese alloy to be used.

The procedures used for reducing each of the metals to particulate form for use in the invention do not constitute a part of the invention, although it appears to be necessary to use the magnesium-base magnesium-manganese alloy in atomized rather than other subdivided form. The atomized form has an extremely fine grain because the individual atomized particles are quickly solidified from small drops of molten metal.

The metals in the particulate form described are mixed together to form a uniform mixture of the metal particles. The proportions may be varied to suit the end in view, the proportion of magnesium-soluble metal, including the aluminum added, being from about 0.1 to 12 per cent by weight of the mixture. The mixture is charged into the heated container of a ram extruder having a suitable size container and die opening and subjected to extrusion pressure to cause the heated metal mixture to be compacted and expressed through the die opening.

The temperature of the metal mixture in the container may be the same as that conventionally employed for extruding the known magnesiumbase magnesium-manganese alloys, e. g. from about 500 to 1000 F., the usual temperature being about 600 to 750 F. The ratio of the crosssectional area of the extrusion container to that of the die opening has a material efiect on the mechanical properties of the extrusion product obtained. A desirable ratio is at least about to 1, although ratios as high as 150 to 1 or more may be used.

The rate of die-expression depends to some extent upon the size and shape of the die as well as the temperature of operation and is to be held down to that at which the extrusion produced is free from hot shortness. In general, the properties of the product are better at low extrusion speeds, e. g. 3-7 feet per minute. A safe extrusion speed may be ascertained by visual examination of the product as it extrudes, the hot shortness being evident as cracks in the extruded product and sharply reduced strength.

The extruded composite product obtained has the same degree of compactness and integrity as the usual magnesium-base alloy extrusion made from a solid mass, such as an ingot of a magnesium-base alloy and may be worked as by rolling, forging, pressing, drawing, etc., although the metallographic structure of the composite product is uniquely difierent from the conventional magnesium-base alloy extrusion. Metallographic examination of the composite product reveals a new type of structure in a magnesiumbase alloy article. The structure is essentially multimetallic, being composed of innumerable elongated particles of each of the particulate forms of the metals in the extrusion mixture. The elongated particles are oriented with the long axis of the particles parallel to that of the extrusion. The elongated metal particles are all welded one to the other without voids. There is difiusion of some of the aluminum constituent of the aluminum-containing particles into the magnesium-base magnesium-manganese alloy particles and precipitation thereby of manganese therein; other magnesium-soluble metal, if present, also more or less difiuses into the particles of magnesium-base magnesium-manganese alloy; and there is some diffusion of magnesium from the magnesium-base magnesium-manganese alloy particles into the aluminum and other magnesium-soluble metal particles, if present, forming composite alloy. The mechanical properties of the composite extrusion obtained generally surpass those otherwise obtainable in a magnesium-base magnesium-manganese alloy. Moreover, the ratio of the amount of aluminum to manganese need not be limited by the incompatibility exhibited by these metals in conventional fusion alloying. A generally higher than conventional amount of manganese can be present in the composite product of the invention than can be tolerated in the conventional magnesium-base magnesium-manganese alloy, with beneficial results as regards mechanical and other properties.

The invention may be further illustrated and explained in connection with the accompanying drawing in which:

Fig. 1 shows a schematic sectional elevation of an extrusion apparatus suitable for use in practicing the invention.

Fig. 2 is a similar view to Fig. 1 showing a modification of the apparatus: and

Fig. 3 is a similar view to Fig. 1 showing another modification of the apparatus.

As shown, the apparatus comprises, in its three forms, an extrusion container l adapted to confine a charge 2 of the mixture of metal particles to be compacted and extruded. The container is provided with a heating element 3. In Fig. 1, one end of the container l is closed by the die plate 4 in which is provided the die opening 5. In this form of the apparatus, the charge 2 is caused to be compacted in the container and extruded through the die opening 5 by application of pressure by means of the dummy block 8 forced into the bore 1 of the container by the ram 8 to form the extrusion 9.

In the form of the apparatus shown in Fig. 2, the container l is closed at one end by the plate [0. The other end of the container receives the die block ll carried by the hollow ram 12 which forces the die block into the contamer causing the charge 2 to be compacted and to extrude through die opening l3 to form the extrusion I 4 which extends into bore 15 of the hollow ram l2.

In the modification of Fig. 3, the container is closed at one end with a plate IS. The charge 2 is extruded as a tubular extrusion I! through the annulus [8 around the die block l9 while it is forced into the container by the ram 20.

The forms of the apparatus shown are conventional.

By putting a charge of the mixture of the metals involved under pressure while at heat as with the apparatus shown, the mixture of readymentioned.

The following examples. are illustrative. of the invention-z.

97 parts by weight of atomized particles of a binary magnesium-base alloy containing 1.08

per cent of manganese, passing through a. 20 mesh sieve and being retained on a 200- mesh sieve, are mixed with 3 parts by weight of mechanically comminuted aluminum-havingaparticle size below passing through a 200 mesh sieve. The mixture is charged into an extrusion press container of an apparatus of the type illustrated. The container is heated to 750 F. The ratio of the area of the die opening to that of the container. is 50; to 1. Extrusion pressure is applied, thereby compacting the charge which extrudes as the compacting pressure is increased to about 40,000 p. s. i'. The rate of extrusion is held to about 5 feet per minute with a die temperature of 630 F. The extrusion obtained conand. of magnesium into. the surface of the; elongated aluminumv particles as: Well as precipitation of some manganese-aluminum. compound in. the binary magnesium-manganesealloy particles near the boundaries demarking the two kinds of metal particles. of. the extrusion charge. I

The tensile. yield strength. of. the extrusion. is

40,000 pounds per square inch (the tensile yield strength is the stress in pounds per square inch at which the.- stress-strain curve. deviates 0.2 per. cent from the modulus line)... For comparison, the same atomized binary magnesium-base magnesium-manganese alloy extruded alone under the same conditions of temperature, ratio of reduction in area, and extrusion speed has a tensile yield strength of 32,000 pounds per square inch.

The extent of the diffusion and precipitation which occurs in the composite product may be affected by heat treatment following the extrusion operation, generally with beneficial results as regards strength. As illustrative of this, the extrusion product of. the foregoing example was aged by heating for 16.- hours at 350 F. as a result its. tensile yield strength was increased, to 42,000 p. s. i.

6 EXAMPLE 2 9'7; partsby weight of atomized particles; of'a binary magnesium-base alloy containing Ldper cent of manganese, the. balance being magnesium, passing through a 20 mesh sieve and being retainedon a 200': mesh. sieve areuniformly mixed-with 3 partsb-y weight of aluminum powderpassing through a 200-mesh sieve. Themixture is; directly: extruded using apparatus like that: of Fig. 1, at- 600 F2 through a die opening 0.375: inch in diameter producing a round extrusion at the rate of five feet of extrusion per minute. The tensile yield strength of the-extruded product: is 38,000 p. s. i. On heat treatingby heating for 1 hour at: 750 F. followed by heating for 1 6 hours-at 350 Fi, the tensile yield strengtl'i increases: to: 41,000 p. s. i. For" comparison, the same atomized binary magnesiumbase magnesium-manganese alloy as used in the foregoing mixture extruded alone using the samevapparatus and other conditions of extrusion produces an extrusion having a tensile yield strength of 30,000 p. s. i. On subjecting this, extrusion to the same heat treatment as git/.6111 the composite extrusion, the tensile yield strength declinesto 27,000 p. s. i.

EXAMPLE 3 97 parts by weight of atomized particles of a magnesium-base alloy containing 1.81 per cent of manganese, 0.6 per cent of calcium, the balance being magnesium, passing a 20 mesh sieve and being retained upon a 200 mesh sieve are mixed with 3gper cent by weight of aluminum powder passing 200 mesh. The mixture is extruded at 65.0" F. into strip inch thick and 4; inch wide. The extrusion is then heated to 700 E': and rolledintwo. passes at. this tempera..- ture: producing; a reduction in thickness. of' 30 per cent each... The as-rolled strip. product. has a tensile yield strength of 39,400 p. s. i.v with. an elongation of 6.5 per cent. For comparison, the same atomized magnesium-base alloy extruded alone and rolled under the same conditions of extrusion and rolling has a tensile yield strength of 24,000 p. s. i. with an elongation of 6 per cent.

Although the aluminum constituent may be in commercially pure. form, as. in the foregoing examples, ithas been found that a smoother surface is obtained on the extruded product. by alloying the aluminum with magnesium before comminuting to. produce; the aluminum-containi'ng particles for use in the invention. Examples: 4-, 5, 6 and, 7. are illustrative ofthe' use of alloyed. aluminum. inthe invention.

An atomized magnesium-base magnesiummanganese" alloy; containing 1.71 per cent man;- ganese, in particles passing through a 20 mesh sieve and being retained. on..a 200 mesh sieve, is mixed with an equal weight of a comminuteds magnesium-base binary magnesiumalurninum; alloy containing 6. per centiof' aluminum. The. aluminum-containing alloy particles pass: throu h a 200 mesh. sieve. The mixture is heated tov 650 and extruded at. this. temperavtime. It a: solid; extrusion having an average. content of aluminum of about 3 per cent. by weight and ofmanganese. of about 0.85 per cent by weight; Its tensile strength is 43,000 p. s. i.. as extruded. For comparison,v an atomized magnesium-base magnesium-manganeseal-loy, containing; 1.7 per. cent of, manganese having particles passing a 20 mesh. sieve and remaining on a 200 mesh' sieve, on being extruded alone, under the same conditions, yields an extrusion having a tensile strength of 41,000 p. s. i.

EXAMPLE 7 In this example, the atomized magnesiummanganese alloy used contained 1.77 per cent of manganese, the balance being magnesium. It

EXAMILE a was mixed with comminuted magnesium-alumi- An atomized magnesium-base alloy containnum eutectic (same composition as that used in ing 1.77 per cent of manganese, the balance be Example 6) in various proportions and the mixing magnesium, is mixed with a comminuted tures were extruded into a composite alloy wire binary alloy consisting of 80 parts of magnesium 0.092 inch in diameter at the rate of about two and parts of aluminum, in various propor- 10 feet of wire per minute. The extrusion charge .tions and the mixtures are extruded into a was at about 800 F. and the die about 680 F. composite alloy wire 0.092 inch in diameter with The proportions of the two alloys in the extrua reduction in area of 29 to 1. Each mixture sion charge and the properties of the composite is at about 800 F. and the die at about 680 F. extrusions obtained are set forth in Table II The as-extruded tensile strength (TS) and ten- 10 together with the properties of the extrusion sile yield strength (TYS) in 1000's of pounds per of the atomized magnesium-base magnesiumsquare inch of the resulting composite extrumanganese alloy extruded alone for comparison.

Table II Composition of Extrusion Properties 1 trusion Charge, Example? Parts)? Welght ASX Aged H. 'r. H. 'r. .4

Mg-M M -A1 Alloy Eutgecfic TYS 'rs TYS TS TYS TS TYS TS 97 3 30 41 36 44 27 as 31 4o 94 s 32 45 a7 45 29 41 31 41 91 9 34 43 41 35 44 as 46 as 12 35 42 a9 47 45 4s 76 24 45 45 46 4e 46 45 49 64 3e 42 44 4s 49 47 49 100 25 4o 29 41 25 a7 25 as 1 In nearest 1,000 p. s. i.-

ASX =as-extruded.

Aged=heat treated 16 hours at 350 F. H. T.=heat treated 1 hour at 750 F. H. T. A.=heat treated 1 hour at 750 F. followed by heat treating for 16 hours at 350 F.

sions are tabulated in Table I for each proportion of the two alloys in the extrusion charge. A blank of the atomized binary magnesiummanganese alloy similarly extruded is included for comparison in the same table.

Table I minuted form. Example of such metals are gffiggfii E t s i g g- 45 cadmium, lead, manganese, silver, tin, and zinc.

N0 5 Parts y Wt. mu 6 The following examples are illustrative of this:

g g 2,3 TYS TS EXAMPLE 3 98 parts by weight of an atomized magnesium- 33 g 23 base magnesium-manganese, the balance being 85 15 35 45 1.6 per cent of manganese, the balance being 23 2g 23 '2? magnesium, passing a 20 mesh sieve and remain- 40 60 46 54 ing on a 200 mesh sieve, is mixed with 1 part by 1 25 55 weight of comminuted aluminum and 1 part by weight of comminuted cadmium, the aluminum A desirable form in which to employ the magnesium alloyed aluminum according to the invention is as comminuted magnesium-aluminum eutectic. Examples 6 and 7 are illustrative of this.

EXAMPLE 6 88 parts by weight of an atomized magnesiummanganese alloy containing 1.81 per cent of manganese, and 0.6 per cent of calcium, the balance being magnesium, is mixed with 12 parts by weight of the magnesium-aluminum eutectic (67 per cent magnesium, balance aluminum). The mixture is extruded at 600 E. into a strip 95 inch by inch. The strip is rolled in two passes each producing a reduction in thickness of about 30 per cent, the metal being at about 700 F. during the rolling. The tensile strength of the rolled composite alloy product is about 52,000 p. s. i.

EXAMPLE 9 On substituting an equal amount of comminuted lead for the cadmium of Example 8, the solid composite extrusion obtained has a tensile strength of 43,000 p. s. i.

EXAMPLE 10 On substituting an equal amount of comminuted manganeses for the cadmium of Example 8, the solid composite extrusion obtained has a tensile strength of 44,000 p. s. i.

.On substituting an .equal amount of comminu'ted tin for the cadmium o'fExample 8, the solid extrusion obtained has atensile strength of 45,000,;p. s. i. 3 parts of tin similarly usedper 100 ;.parts of the mixture provides {an extrusion having artensilestrength of 45,000p..-s..i.

On substituting an equal amount of comminuted zinc for the cadmium or'Exar-npleflythe solid extrusion obtained has a tensile strength of 48,000 p. s. i.

EXAMPLE 14 On using 3 parts by weight of aluminum and 3 parts by weight of tin instead of 1 part of each of these metals per 100 parts of the mixture, as in Example 12, the solid extrusion obtained has a tensile strength of 45,000 p. s. i.

EXAMPLE 15 The use of two or three comminuted magnesium-soluble metals in the extrusion charge in addition to aluminum in the manner described in Example 8, using a die opening of 0.090 inch and producing a reduction in area of 31:1, is illustrated in the data tabulated in Table III.

l 0 .I'he extruded composi e pr duct of th invention may be subjected to any of the metal tneating or working operat o common to the c. ventional non-compos t mae l s u-m ba e a oy extrusion inclu in :he r atm nt and rolling already mentioned as well as iorging pressm g, and -drawing. If desired, a conventional chemical.or;,other finish may be applied. 1521. product may be electroplated :by methods suitable ,ior

magnesium.

containing aluminum, ther y impr vin tnetensileand other pro erties .of thealloy. .In-addition, other elementary magnesium-alloyable metals may be included in the composition.

We claim:

1. The method of making a solid composite high strength metal article comprising magnesium alloyed with manganese which comprises forming a mixture of an atomized magnesiumbase magnesium-manganese alloy containing from 0.1 to 2.5 per cent of manganese and at least one comminuted magnesium-soluble metal including aluminum, the magnesium-soluble metal comprising between 0.1 and 12 per cent by weight of the mixture, and the magnesium-soluble metal being associated with up to but not more than 4 times its Weight of magnesium, and die-expressing the mixture in solid condition at a temperature above about 500 F.

Table III figffififlgfi? Charge Composite Extrusion Properties 1 x ple 15 M ASX Aged H. T H- T. A.

Magnesium-Soluble Metal TYS TS TYS TS TYS TS TYS TS 97 1 A1 1 Z11 1 Ag 44 47 46 49 40 46 42 47 97 1 A1 1 Zn 1 0(1 42 48 42 47 40 46 40 47 97 1 A1 1 Zn 1 M11 41 46 43 48 41 47 40 47 97 1 A1 1 Zn 1 P1) 41 47 43 48 40 47 40 47 97 1 A] 1 211 1 S11 41 47 44 49 40 46 41 47 96 1 A1 1 Zn 1 Ag 1 Cd 42 48 43 48 41 47 41 47 96 1 A1 1 Zn 1 Ag 1 Mn 39 46 43 48 39 47 40 47 96 1 A1 1 Zn 1 Ag 1 P1) 42 48 44 48 41 46 39 47 96 1 A]. 1 Zn 1 Ag 1 Sn 42 48 43 48 39 47 40 47 1 See footnotes Table II.

1' Same alloy as Blank" in Table II.

The foregoing examples are to be regarded as illustrative rather than limitative as considerable variations may be made in the proportions of the metals in the charge to be extruded and details of operation, such as the temperature, and speed of extrusion, and reduction in area within the scope of the invention. In general, the proportion of magnesium-soluble metal (exclusive of magnesium but including the aluminum) which is mixed with the atomized magnesium-base magnesium-manganese alloy in forming the mixture to be die-expressed, may be as much as about 12 per cent of the weight of the mixture and the proportion of included aluminum being at least 0.1 per cent. A preferred proportion of aluminum in the mixture is about 3 per cent. The other unalloyed magnesium-soluble metals, e. g. cadmium, lead, manganese, silver, tin and zinc, if included, may be used in a proportion between about 0.2 and 3 per cent, a preferred amount being about 1 per cent.

the proportion of magnesium-soluble metal in the mixture is not over about 8 per cent and includes at least about 3 per cent of aluminum said aluminum being alloyed only with magnesium.

4. The method according to claim 1 in which the proportion of magnesium-soluble metal in the mixture is not over about 6 per cent including at least about 3 per cent of aluminum, and about 1 to 3 per cent 'of at least one of the unalloyed metals selected from the group consisting of cadmium, lead, manganese, silver, tin and zinc.

5. The method according to claim 1 in which the atomized magnesium-base magnesium-man- 1 1 gaiiese alloy contains 0.05 to 015 per cent of calmum.

6. A composite metal body comprising two particulate metals one of the metals being a magnesiumbase magnesium-manganese alloy; the other comprising at least one magnesium-soluble metal including aluminum, the magnesium-soluble metal comprising between 0.1 and 12 per cent by Weight of the composite body and the aluminum being associated with up to but not more than 4 times its weight of magnesium, the particles of each metal being elongated, oriented in the same direction, and welded together into an integral solid.

7. A composite metal body according to claim 6 including in addition to the elongated particles of aluminum, elongated particles of one of the magnesium-soluble unalloyed metals selected 12 from the group consisting of cadmium, lead, manganese, silver, tin and zinc.

8. A composite metal body according to claim 6 in which the aluminum is alloyed with mag= nesium. V

THOMAS E. LEONTIS. ROBERT S. BUSK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,024,767 Jefiries et a1. Dec. 17, 1935 2,287,251 Jones June 23, 1942 OTHER REFERENCES Treatise on Powder Metallurgy by Goetzel, v01. 2, pages 500, 740, 741. 1950.

Claims (1)

1. 6. A COMPOSITE METAL BODY COMPRISING TWO PARTICULATE METALS ONE OF THE METALS BEING A MAGNESIUM-BASE MAGNESIUM-MANGANESE ALLOY, THE OTHER COMPRISING AT LEAST ONE MAGNESIUM-SOLUBLE METAL INCLUDING ALUMINUM, THE MAGNESIUM-SOLUBLE METAL COMPRISING BETWEEN 0.1 AND 12 PER CENT BY WEIGHT OF THE COMPOSITE BODY AND THE ALUMINUM

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